Session 2. The Particle Nature of Matter: Solids, Liquids,
and Gases

Learning Goals

During this session, you will have an opportunity to build
understandings to help you:

A liquid (water).

Recognize characteristics of a good scientific model

Understand the macroscopic evidence for each of the
four basic principles of the particle model of matter:

1. Matter is made of tiny particles.
2. There is empty space between the particles.
3. The particles are in constant motion.
4. There are forces that act between the particles

Video Overview

What explanation might account for the differences between
the states of matter, as well as explain its different properties? Session
2 introduces the particle model of matter, the principles which underlie
a wide range of phenomena. By contrasting this model with what is variously
called the continuous, continuum, or plenum model, this session shows how
the particle model is useful for making accurate predictions about a variety
of behaviors of matter on a macroscopic scale.

Video Outline

The video begins by defining what scientists mean by the
term “model,” establishing what
makes a good model, and describing
the process by which models are continually revised. Then, children in
the Science Studio divide a piece of aluminum foil into the smallest pieces
possible and are asked: Is it possible to go on dividing forever? Is there
ever a point at which the pieces no longer have the properties of the aluminum
foil? Science historian Dr. Al Martinez recounts the history of the continuous
model originally proposed by the Greeks, explains its appeal, and later
tries to use this model to explain the expandability and compressibility
of gases.

Back in the Science Studio, children continue to reveal their
models of matter, which support what science education research says
about the difficulty
children sometimes have connecting their
ideas
about macroscopic matter with the particles that make it up. By “taking a trip into a drop
of water,” we then explore the size and scale that make this connection
so challenging. This raises the question, “What’s in between
the particles of matter?”

For an answer, we first explore fifth
graders’ ideas on the subject,
and then visit vacuum engineer Bob Childs, whose work in nuclear fusion
relies on an important principle of the particle model. We return to
the Science Studio one last time, where we find children further developing
their models to explain the compressibility
of gases and proposing
a model
to explain an everyday change of state—boiling.

In Session 2’s
Featured
Classroom segments, Linsey Newton’s
third graders in Hudson, Massachusetts, observe two more changes
of state—evaporation
and condensation—and Russell Springer’s fifth graders
in Newtonville, Massachusetts, try to explain the seemingly random
movement of oil droplets
suspended in water. In both classrooms the students express a variety
of macroscopic rationale for what is happening.